High figure of merit extreme bandgap Al<sub>0.87</sub>Ga<sub>0.13</sub>N-Al<sub>0.64</sub>Ga<sub>0.36</sub>N heterostructures over bulk AlN substrates
Kamal Hussain, Abdullah Mamun, Richard Floyd, Md. Didarul Alam, Michael E. Liao, Kenny Huynh, Yekan Wang, Mark S. Goorsky, M. V. S. Chandrashekhar, G. Simin, Asif Khan
Abstract
Abstract We report on high-quality n -Al 0.87 Ga 0.13 N-A 0.64 Ga 0.36 N heterostructures over single crystal AlN. For these pseudomorphic heterostructures, high-resolution X-ray and X-ray Topographic analysis was used to establish a threading dislocation density of 7 × 10 3 cm −2 . Using reverse composition graded n + -Al x Ga 1- x N contact layers, we obtained linear ohmic contacts with 4.3 Ω mm specific resistance. A critical breakdown field >11 MV cm −1 was also measured. In combination with the channel resistance of 2400 Ω sq −1 , these translate to a Baliga’s Figure of Merit of 2.27 GW cm −2 . This, to the best of our knowledge is the highest reported value for extreme bandgap AlGaN heterostructures.